Actinide tetra-N-heterocyclic carbene ‘sandwiches’

DeJesus, Joseph F.; Kerr, Ryan W. F.; Penchoff, Deborah A.; Carroll, Xian B.; Peterson, Carl R.; Arnold, Polly L.; Jenkins, David M.

doi:10.1039/d1sc01007g

Cited by 11 publications

(19 citation statements)

References 63 publications

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“…From a theoretical viewpoint, an An complex is likely to exhibit a complicated multiconfigurational ground state (GS) because of the open 5f shell. Although Kohn–Sham DFT rests on a single Slater determinant, it is often the method of choice for geometry optimizations and chemical bonding analyses, ,− thermodynamic properties, ,, and even magnetic properties ,, of medium size to large actinide systems. Multiconfigurational wavefunction-based methods, such as complete active-space (CAS) self-consistent field (SCF) approaches, − are well-suited for An chemistry research, especially for susceptibility and NMR calculations, magnetic circular dichroism (MCD), or other areas that require accurate treatment of the unpaired electrons and static correlation. − CAS-level calculations are usually conducted based on crystal structure geometries, if available, or optimized DFT geometries.…”

Section: Introductionmentioning

confidence: 99%

Covalency of Trivalent Actinide Ions with Different Donor Ligands: Do Density Functional and Multiconfigurational Wavefunction Calculations Corroborate the Observed “Breaks”?

Sergentu

Feng

et al. 2021

Inorg. Chem.

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A comprehensive ab initio study of periodic actinide−ligand bonding trends for trivalent actinides is performed. Relativistic density functional theory (DFT) and complete activespace (CAS) self-consistent field wavefunction calculations are used to dissect the chemical bonding in the [AnCl 6 ] 3− , [An-(CN) 6 ] 3− , [An(NCS) 6 ] 3− , [An(S 2 PMe 2 ) 3 ], [An(DPA) 3 ] 3− , and [An(HOPO)] − series of actinide (An = U−Es) complexes. Except for some differences for the early actinide complexes with DPA, bond orders and excess 5f-shell populations from donation bonding show qualitatively similar trends in 5f n active-space CAS vs DFT calculations. The influence of spin−orbit coupling on donation bonding is small for the tested systems. Along the actinide series, chemically soft vs chemically harder ligands exhibit clear differences in bonding trends. There are pronounced changes in the 5f populations when moving from Pu to Am or Cm, which correlate with previously noted "breaks" in chemical trends. Bonding involving 5f becomes very weak beyond Cm/Bk. We propose that Cm(III) is a borderline case among the trivalent actinides that can be meaningfully considered to be involved in ground-state 5f covalent bonding.

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Section: Introductionmentioning

confidence: 99%

Covalency of Trivalent Actinide Ions with Different Donor Ligands: Do Density Functional and Multiconfigurational Wavefunction Calculations Corroborate the Observed “Breaks”?

Sergentu

Feng

et al. 2021

Inorg. Chem.

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“…This strategy has allowed the isolation of a number of interesting metal complexes 46 − 49 of the early transition metals, 50 − 71 the lanthanides, 72 − 80 and the actinides. 81 − 86 …”

Section: Introductionmentioning

confidence: 99%

“…However, this weak bond may be enhanced by harnessing anionic linkers. This strategy has allowed the isolation of a number of interesting metal complexes − of the early transition metals, − the lanthanides, − and the actinides. − …”

Section: Introductionmentioning

confidence: 99%

Mesoionic Carbenes in Low- to High-Valent Vanadium Chemistry

et al. 2021

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We report the synthesis of vanadium(V) oxo complex 1 with a pincer-type dianionic mesoionic carbene (MIC) ligand L 1 and the general formula [VOCl(L 1 )]. A comparison of the structural (SC-XRD), electronic (UV–vis), and electrochemical (cyclic voltammetry) properties of 1 with the benzimidazolinylidene congener 2 (general formula [VOCl(L 2 )]) shows that the MIC is a stronger donor also for early transition metals with low d-electron population. Since electrochemical studies revealed both complexes to be reversibly reduced, the stronger donor character of MICs was not only demonstrated for the vanadium(V) but also for the vanadium(IV) oxidation state by isolating the reduced vanadium(IV) complexes [Co(Cp*) 2 ][1] and [Co(Cp*) 2 ][2] ([Co(Cp*) 2 ] = decamethylcobaltocenium). The electronic structures of the compounds were investigated by computational methods. Complex 1 was found to be a moderate precursor for salt metathesis reactions, showing selective reactivity toward phenolates or secondary amides, but not toward primary amides and phosphides, thiophenols, or aryls/alkyls donors. Deoxygenation with electron-rich phosphines failed to give the desired vanadium(III) complex. However, treatment of the deprotonated ligand precursor with vanadium(III) trichloride resulted in the clean formation of the corresponding MIC vanadium(III) complex 6 , which undergoes a clean two-electron oxidation with organic azides yielding the corresponding imido complexes. The reaction with TMS-N 3 did not afford a nitrido complex, but instead the imido complex 10 . This study reveals that, contrary to popular belief, MICs are capable of supporting early transition-metal complexes in a variety of oxidation states, thus making them promising candidates for the activation of small molecules and redox catalysis.

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“…We previously reported that a direct deprotonation approach, as opposed to transmetalation, was required to synthesize metal complexes of H 4 ( BMe 2 ,Me TC H )(Br) 2 . − Unlike examples with transition metals, our attempts to form the target lanthanide complexes with n BuLi, LiN i Pr 2 , or KN i Pr 2 as the base were unsuccessful. − ,− The deprotonation of H 4 ( BMe 2 ,Me TC H )(Br) 2 in dimethoxyethane with NaN(SiMe 3 ) 2 (NaHMDS) at −35 °C, followed by the addition of anhydrous LuBr 3 , with subsequent heating at 50 °C for 24 h yielded ( BMe 2 ,Me TC H )Lu(HMDS) ( 1 ) in 22% isolated yield after recrystallization from pentane, as shown in Scheme (top). This synthetic approach is similar to our synthesis of actinide “sandwich” complexes such as ( BMe 2 ,Me TC H ) 2 U . This reaction was also successful with other solvents such as pyridine, CH 3 CN, and t BuCN, albeit with reduced yields.…”

Section: Results and Discussionmentioning

confidence: 99%

“…Our group has previously reported the synthesis of dianionic tetra-NHC macrocycles for transition metals such as iron and chromium − and very recently actinides, including uranium and thorium . Thus, we thought that these anionic tetra-NHC macrocycles would be suitable candidates to ligate to lanthanides.…”

Section: Introductionmentioning

confidence: 99%

Late Lanthanide Macrocyclic Tetra-NHC Complexes

et al. 2022

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An isostructural set of macrocyclic tetra-N-heterocyclic carbene (NHC) complexes were synthesized on late lanthanides including Lu, Yb, Ho, Dy, and Gd. They were characterized by single-crystal X-ray diffraction, multinuclear NMR, electrochemistry, and SQUID magnetometry. Solid-state structures show that all complexes are in a highly distorted squarepyramidal geometry with an axial HMDS ligand. 1 H NMR for Lu, Yb, and Dy demonstrates that these geometries are maintained in solution. Electrochemical measurements on the Yb complex show that the NHCs are very strong σ-donors compared to other organometallic Yb complexes. Magnetic measurements of the Yb and Dy complexes reveal slow relaxation of the magnetization in both complexes. The highly anisotropic Dy complex possesses an energy barrier to spin reversal of 52.42 K/36.43 cm −1 and waistrestricted hysteresis up to 2.8 K. Finally, an 18-atom macrocycle variant of the Lu complex was synthesized for comparison in reactivity and stability. These complexes are the first lanthanides prepared with macrocyclic NHCs and suggest that NHCs may be a promising ligand for developing single-molecule magnets.

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Actinide tetra-N-heterocyclic carbene ‘sandwiches’

Abstract: Highly-symmetrical, thorium and uranium octakis-carbene ‘sandwich’ complexes have been prepared by ‘sandwiching’ the An(iv) cations between two anionic macrocyclic tetra-NHC ligands, one with sixteen atoms and the other with eighteen atoms.

Cited by 11 publications

References 63 publications

Covalency of Trivalent Actinide Ions with Different Donor Ligands: Do Density Functional and Multiconfigurational Wavefunction Calculations Corroborate the Observed “Breaks”?

Covalency of Trivalent Actinide Ions with Different Donor Ligands: Do Density Functional and Multiconfigurational Wavefunction Calculations Corroborate the Observed “Breaks”?

Mesoionic Carbenes in Low- to High-Valent Vanadium Chemistry

Late Lanthanide Macrocyclic Tetra-NHC Complexes

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